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What doctors can't see can make glioblastoma especially difficult to treat.
This aggressive brain cancer can extend beyond what's visible on a standard MRI, making it difficult to precisely target treatment. Just 5% to 7% of patients survive five years after diagnosis.
Mayo Clinic researchers are studying advanced imaging techniques designed to bring more of the tumor into view and potentially give care teams a better-defined target.
"We're trying to develop and improve treatments that will help extend the length of time patients live, as well as their quality of life and function while they're alive," says Dr. William Breen, a radiation oncologist at Mayo Clinic. "From a radiation perspective, we need to be able to accurately see the tumor to accurately target it and treat it as well as possible."
Journalists: Broadcast-quality video (1:04) is in the downloads at the end of this post. Please courtesy: "Mayo Clinic News Network." Read the script.
Seeing tumors more clearly
A standard MRI with contrast shows doctors where glioblastoma appears to be, but tumor cells can extend into the surrounding brain beyond what is clearly visible.
"In over half of patients, we find a tumor more than a centimeter beyond the standard MRI-defined tumor, and in 20% of patients, we find a tumor more than 2 centimeters beyond the standard MRI-identified tumor," Dr. Breen says.
To see more, Mayo Clinic investigators are combining advanced MRI techniques with research PET scans. The scans provide different clues, such as areas where cells are especially dense, where blood flow is increased or where there may be more aggressive tumor activity.
Together, they can give doctors a more detailed picture of the tumor and where it may extend.
Treating tumors more precisely and effectively
Because glioblastoma can extend beyond what doctors see on a traditional MRI, radiation treatment generally includes an extra margin around the visible tumor to help cover cancer cells that may be hidden.
Advanced imaging could help doctors more accurately identify those areas and tailor radiation accordingly. For some patients, that could mean treating a smaller area of the brain and reducing radiation exposure to healthy tissue.
"By using advanced imaging, we're able to treat a smaller area in many patients and reduce the amount of normal brain receiving radiation, which may make for a safer and better treatment," Dr. Breen says.
Researchers also are studying whether they can direct more intensive treatment toward areas that advanced imaging identifies as particularly concerning.
Greater precision may make it possible to give a higher dose of radiation at each treatment and finish therapy sooner. Dr. Breen says treatment has been shortened from three to six weeks to one to two weeks for some patients, meaning fewer trips to the hospital and more time at home.
Bringing specialties together
The research brings together experts across Mayo Clinic, including neurosurgeons, radiation oncologists, neuro-oncologists, neuroradiologists and nuclear medicine specialists.
"I think our strength at Mayo Clinic for treating glioblastoma is the multidisciplinary team," Dr. Breen says.
While glioblastoma remains challenging to treat, advances in imaging, surgery, radiation, chemotherapy and other therapies are helping researchers continue to improve care.
"We know there's still much progress to be made," Dr. Breen says, "but we have seen progress over the years to improve both quality of life and quantity of life for our patients with glioblastomas."
